New silyl-functionalized BisGMA provides autonomous strengthening without leaching for dental adhesives

Abstract

Resin-based composite has overtaken dental amalgam as the most popular material for direct restorative dentistry. In spite of this popularity the clinical lifetime of composite restorations is threatened by recurrent decay. Degradation of the adhesive leads to gaps at the composite/tooth interface—bacteria, bacterial by-products and fluids infiltrate the gaps leading to recurrent decay and composite restoration failure. The durability of resin-dentin bonds is a major problem. We address this problem by synthesizing silyl-functionalized BisGMA (e.g., silyl-BisGMA), formulating dental adhesives with the new monomer and determining the physicochemical properties and leaching characteristics of the silyl-BisGMA adhesives. Silyl-BisGMA was synthesized by stoichiometric amounts of BisGMA and 3-isocyanatopropyl trimethoxysilane (IPTMS). The control adhesive was a mixture based on HEMA/BisGMA (45/55, w/w). In the experimental formulations, BisGMA was partially or completely replaced by silyl-BisGMA. Water miscibility, polymerization behavior (Fourier transform infrared spectroscopy, FTIR), thermal property (modulated differential scanning calorimetry, MDSC), mechanical properties in dry and wet conditions (dynamic mechanical analysis, DMA), and leached species (HPLC) were investigated. Data from all tests were submitted to appropriate statistical analysis (α = 0.05). Silyl-BisGMA-containing adhesives exhibited comparable water miscibility, lower viscosities, and significantly improved degree of conversion of C=C bond as compared to the control. After 4 weeks aqueous aging, the glass transition temperature and rubbery moduli of the experimental copolymers were significantly greater than the control (p<0.05). HPLC results indicated a substantial reduction of leached HEMA (up to 99 wt%) and BisGMA (up to 90 wt%). By introducing silyl-functional group, the new BisGMA derivative exhibited potential as a monomer that can lead to dental adhesives with improved mechanical properties and reduced leaching under conditions relevant to the oral environment.

Evolution of Network Structure and Mechanical Properties in Autonomous-Strengthening Dental Adhesive

“…We reported that the self-strengthening reaction is accelerated not only by heating but also by water [ 8 , 9 , 11 ]. The rubbery moduli and T g for the treated E1 increased significantly after one day of aqueous aging.…”

“…Although studies have shown improved properties for dental adhesives that achieve autonomous strengthening [ 8 , 9 , 11 , 12 ], little is known about the effect of this reaction on the cyclic-loading response during the early stages of network structure development. Within the clinical environment, the d/a interface will be subjected to cyclic stress and these stresses challenge both the durability of the adhesive and the integrity of the d/a interface [ 31 , 48 ].…”

Threats to adhesive/dentin interfacial integrity and next generation bio‐enabled multifunctional adhesives

“…The increase in mechanical properties following aqueous aging and the significant decrease in leached HEMA reflect a resistance to hydrolysis in the silyl‐BisGMA adhesive formulations. The introduction of silyl‐BisGMA in the adhesive formulation led to higher crosslinked networks as compared to BisGMA/HEMA formulations . The higher crosslinked networks are envisioned as an important component of a multi‐factorial approach to durable adhesives.…”

“…In the MPS‐containing formulations, the rate of hydrolysis of the trialkoxysilyl group is relatively slow as compared to the free radical polymerization of the CC bonds in the methacrylate monomers. The autonomic sol–gel reaction provided a slow and continued reaction, which can gradually generate the SiOSi bond and resist hydrolytic degradation …”

Influences of Polymeric Magnetic Encapsulated Nanoparticles on the Adhesive Layer for Composite Materials Used for Class I Dental Fillings

“…Adhesive composite restorations are threatened by secondary caries, the degradation of the adhesive layer present at the interface between the tooth and by the various defective restorationmaterials, which will then be infested by fluids, bacteria and secondary bacterial products, leading ultimately to the failure of the composite filling. Therefore the durability over time of the connections between dentin and adhesives become an issue [3].…”